New York's main contract, West Texas Intermediate for delivery in October, eased 26 cents to USD 108.28 in mid-morning trade, while Brent North Sea crude for October gained 12 cents to USD 115.80.

Market jitters over Syria resurfaced after Republican House Speaker John Boehner and his right hand man Eric Cantor said they would support a strike against the Assad regime over its alleged use of chemical weapons.

The move was a rare gesture of unity in a divided Congress and left US President Barack Obama hopeful of securing a vote for action from lawmakers next week.

Investors fear US intervention could lead to a wider conflict in the politically volatile Middle East, a key source of the world's crude oil supplies.

Oil prices have tumbled from multi-month highs after Obama said he would seek approval from Congress for military action. They had soared on speculation of imminent US strikes.